Maria Shriver Files For Divorce From Arnold Schwarzenegger

(TMZ) TMZ has learned Maria Shriver has pulled the trigger on her marriage ... she just filed for divorce from Arnold Schwarzenegger ... and we've learned, there is no prenup.

In the divorce petition, obtained by TMZ, Shriver cites "irreconcilable differences" as her reason for ending the 25-year marriage.

Shriver is asking for spousal support and wants the judge to deny Arnold the right to ask for support for himself-- though it's highly unlikely he would.

Shriver is asking for joint custody of their minor children, who she names in the document as 17-year-old "Patrick Arnold Shriver Schwarzenegger" and 13-year-old "Christopher Sargent Shriver Schwarzenegger."

And, in the petition, filed by disso-queen Laura Wasser, Shriver is asking Arnold to pay the attorneys fees of both parties.

As for the date Arnold and Maria separated ... it isn't specified in the divorce papers. more on this story